In related art, a parking brake is used to restrict movement of a vehicle when parking the vehicle, and the parking brake is, for example, a manual brake in which a brake cable is pulled by an operating lever and an operating force is thus transmitted to a brake mechanism, or an electric brake in which a rotational force of a motor is transmitted to a brake mechanism.
With the EPB that is the electric parking brake, at a time of locking, a motor is caused to rotate to a lock side (rotation in a positive direction) and a motor rotational force is transmitted to a brake mechanism (an actuator). At the same time, a motor drive is stopped in a state in which the braking force is generated. At a time of release, the motor is caused to rotate to a release side (rotation in a negative direction) and the braking force is thus released. The generation and release of the braking force is performed by performing this type of lock control and release control.
Note that generally, in a normal service brake, when the braking force is generated by hydraulic pressure, piston return is performed by deformation of a seal member, which is disposed between a piston (corresponding to a pressing member) inside a wheel cylinder (hereinafter referred to as a W/C) and the body. However, when the piston is moved by the EPB such that a brake pad is caused to come into contact with a brake disc, deformation of the seal member is insufficient because the hydraulic pressure is not applied to the seal member at the time of movement. As a result, a problem arises in which a pullback amount of the piston is insufficient when release control is performed.
In relation to this, PTL 1 discloses an electric brake system in which, when the piston of the W/C is pulled back, a return amount in a direction of separation from the disc is performed by operation of the electric brake, irrespective of the seal member, such that instability of the pullback amount can be inhibited.